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Member Post posted an update
Got a Daikin WWV water cooled screw chiller throwing an MHP (mechanical high pressure) fault. Most recent trip was this past Friday. The chiller was operating well upon inspection today with the desired LWT and no active alarms. The MHP fault appears to have occurred intermittently a few times over the last several months per the event log. Diagnostics on pressures temps etc gave no indication of compressor or condenser issues that may have caused the MHP trip.
What do you guys think? This ring any bells in terms of an explanation for the intermittent MHP fault?
Member Post, Member Post and 4 others6 Comments-
Not sure where your located, but Have you guys been having power issues? Is it possible that you could be having an issue with the condenser pump, or tower fan?
Not sure how often the trend is recorded, could it be happening between?
You could upload a log sheet so we could take a look at the data, but could be a power / something shutting down.
Let us know
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@the-chiller-guys getting logs tomorrow morning! Thanks and will keep you updated
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@crockarot44 sounds good brother, let us know.
the more info the better
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@the-chiller-guys apologies for the delayed follow up. Here’s the alarm log snapshot– we are referring to the top (latest) entry. As you will see, probably the only thing that stands out is VFD Current in being 0. However, what isn’t entirely clear to me is if this is a reference to current into the VFD itself or current from the VFD into the compressor. One would surely like to think they mean current actually feeding into the VFD, but there’s no legend or key that provides a definitive description of the nomenclature, and I’ve seen far too many OEM manuals that are guilty of ambiguity on things like this. In any event, it looks to me like there was a power loss event to the VFD and this caused the MHP trip. And speaking of ambiguous nomenclature, without consulting the IOMs one would read “mechanical high pressure” fault and assume the discharge or liquid pressure exceeded a certain threshold; however, Daikin’s listed trigger for this event is as follows:
“At least 12 seconds elapsed since controller booted and compressor VFD reports Safe Stop alarm or warning.”
To me, in view of how this event is defined, and seeing as the alarm snapshot is telling us there was no VFD current in, I think we’re looking at intermittent power supply problems.
If so, could this be rectified by surge protection? I’ve only ever added that to communicating systems or mini splits to protect inverters, so while VFDs are a different puppy, it strikes me as conceivable that surge protection might be both usable and useful here.
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@crockarot44 What kind of drive is on this one?
I worked on a ton of AWV’s, but only a couple of their guinea pig WWV’s when they first came out.
They both used Yaskawa drives.
Can you take a look at the fault history on the drive?
A surge protector will only help with voltage spikes. There are some other solutions if it is the power supply, but you need to know what’s going on before I would say to just add something.1 -
So is this the chiller with free cooling coils ? If it is have you cleaned the refrigerant side condenser coils under the free cooling coils.
It’s not easy and a real pita. Both are microchannel . Be careful and a poor design
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